CN110714188A - Surface nanocrystallization high-energy ion injection and permeation composite treatment method - Google Patents

Abstract

The invention relates to the technical field of surface strengthening, in particular to a surface nanocrystallization high-energy ion injection and permeation composite treatment method, which comprises the steps of pretreating the surface of a sample before rolling, firstly cutting an iron plate into cylinders by utilizing linear cutting; fixing a sample on a grinding machine, polishing, firstly polishing the sample flatness on one surface of the sample until the surface is flat, then polishing the surface flatness on the other surface, and finally performing fine grinding treatment on the surface to reduce the roughness of a rolled surface; the mechanical surface modification strengthening technology and the chemical surface modification strengthening technology are applied to the surface of the metal mold in a composite mode, the hardness and the wear resistance of the surface of the mold are obviously improved, the core part keeps the toughness of the original steel matrix, and a gradient transition area with gradually changed performance exists between the surface layer and the core part, so that material damage possibly caused by performance mutation can be effectively avoided, and the service life of the mold is greatly prolonged.

Description

Surface nanocrystallization high-energy ion injection and permeation composite treatment method

Technical Field

The invention relates to the technical field of surface strengthening, in particular to a surface nanocrystallization high-energy ion injection and permeation composite treatment method.

Background

The mould is important technological equipment for production in industries such as machinery, electronics, light industry, national defense and the like, and the quality and benefit of a product and the development capability of a new product are determined to a great extent by the level of the production technology of the mould. The failure of the mold tends to start at the mold surface, and thus the quality of the mold surface performance directly affects the service and life of the mold. The surface modification technology is an important means for improving the surface performance of materials, and is widely applied to occasions requiring wear resistance, corrosion resistance and the like.

The metal surface nanocrystallization technology is characterized in that an external load is applied to the surface of a material repeatedly, the free energy of the surface of a polycrystalline metal material is increased, and the surface tissue generates strong plastic deformation in different directions to gradually thin the coarse-grained structure of the surface layer of the material to a nanometer level. After the nano-structure is formed, the hardness of the composite layer is further improved due to the existence of the gradient nano-structure, so that the friction performance of the material is obviously improved. The technology has the advantages of simple process, low cost and easy realization; the nano-layer structure is compact, and the chemical components are the same as those of the matrix; the nano layer has a gradient structure and is not easy to peel off. The prior successful material surface nanocrystallization method comprises the following steps: mechanical surface grinding (SMAT), ultrasonic shot blasting (USSP), pneumatic shot blasting (AB-SP), ultrasonic shot blasting (SFPB), rotational roll plastic deformation (CRPD), and ultrasonic impact technique (USRP).

The high-energy ion implantation technology (HEII) is to implant high-energy ions into the surface of a material to obtain a new alloy phase beneficial to improving the performance, so that the physical, chemical and mechanical properties of the surface layer of the material are changed. It has been found that the hardness, wear resistance and corrosion resistance of certain metal materials can be significantly improved by High Energy Ion Implantation (HEII). Although the surface modification technology is various, after the surface modification is carried out by high-energy ion implantation, a new alloy phase which cannot be obtained by other methods can be obtained, and the new alloy phase is firmly combined with a substrate without obvious interface and shedding phenomena, so that the problems of adhesion and mismatch of thermal expansion coefficients in a plurality of coating technologies are solved, and certain defects exist in the thickness and uniformity of an impregnation layer.

Disclosure of Invention

In order to solve the problems, the invention provides a surface nano high-energy ion injection-infiltration composite treatment method based on ultrasonic surface rolling and high-energy ion injection-infiltration of tungsten carbide.

The technical problem to be solved by the invention is realized by adopting the following technical scheme:

a surface nano high-energy ion injection-infiltration composite treatment method comprises the following steps:

(1) pretreatment before rolling of sample surface

Firstly, cutting an iron plate into a cylinder with the diameter of 10mm and the thickness of 12mm by utilizing wire cutting;

fixing a sample on a grinding machine, polishing, firstly polishing the sample flatness on one surface of the sample until the surface is flat, then polishing the surface flatness on the other surface, and finally performing fine grinding treatment on the surface to reduce the roughness of a rolled surface;

(2) ultrasonic rolling treatment of sample surface

Fixing the sample treated in the step (1) on a machine tool, and adjusting the coaxiality and the flatness of the sample;

firstly, operating a machine tool to enable a sample to do rotary motion, then starting rolling equipment to set corresponding parameters, waiting for about 5 minutes to enable the vibration frequency of ultrasonic equipment to reach a positive sine wave form, and finally applying pressure to a rolling head, wherein the machine tool parameters are 2-10A, the rotating speed of a main shaft of the machine tool is 100r/min, the feeding speed of the machine tool is 0.1mm/r, the vibration frequency of the ultrasonic equipment is 20-27KHz, the amplitude is 6.5-7.5 mu m, and the pressure applied by the rolling head is 300N;

(3) preparation of tungsten carbide composite layer

Drilling the workpiece processed in the step (2), and suspending the workpiece in an injection infiltration furnace by using an iron wire to penetrate through the hollow hole;

the voltage is adjusted to 600V to keep the temperature in the furnace at the proper temperature of 470 ℃, so that not only can a good infiltration injection effect be achieved, but also the crystal grains of the workpiece can not be coarse;

the heat preservation time is 24 h.

Compared with the prior art, the invention has the beneficial effects that: the invention relates to a surface nano high-energy ion injection-permeation composite treatment method,

(1) the ultrasonic impact treatment can refine crystal grains, and after the nano treatment, the hardness of a composite layer is further improved due to the existence of a gradient nano structure, so that the friction performance of the material is obviously improved.

(2) Researches show that after the ultrasonic rolling pretreatment and the high-energy ion tungsten carbide impregnation, the obtained surface composite layer has thicker hardness and better uniformity and hardness.

(3) The mechanical surface modification strengthening technology and the chemical surface modification strengthening technology are applied to the surface of the metal mold in a composite mode, the hardness and the wear resistance of the surface of the mold are obviously improved, the core part keeps the toughness of the original steel matrix, and a gradient transition area with gradually changed performance exists between the surface layer and the core part, so that material damage possibly caused by performance mutation can be effectively avoided, and the service life of the mold is greatly prolonged.

Drawings

FIG. 1 is a simplified schematic diagram of the ultrasonic surface rolling principle;

FIG. 2(a) is a surface SEM photograph of a sample of example 1;

FIG. 2(b) is a surface SEM image of a sample of example 2;

FIG. 3(a) is a sectional SEM photograph of a sample of example 1;

FIG. 3(b) is a cross-sectional SEM image of a sample of example 2;

fig. 4 is a cross-sectional hardness plot for the example 1 sample and the example 2 sample.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The material selected in the test is Dievar hot work die steel, and the microstructure of the material is hypereutectoid steel ledeburite phase. The main chemical components are Cr, Mo and V.

The alloy components and the basic mechanical properties of the material are shown in tables 1 and 2, respectively.

Table 1 alloy composition of materials

TABLE 2 mechanical Properties of Dievar Hot work die steels

Example 1

The preparation work before ultrasonic surface rolling treatment comprises the steps of polishing the surface of a material by using a grinding wheel;

the technological parameters of the test equipment, such as the amplitude of the impact head, the static load applied to the surface of the plate, the rotating speed of the plate, the transverse feeding speed of the impact head and the like, are continuously adjusted through a large number of tests, the rolling effect of the sample is compared, and the optimal technological parameters are selected to prepare the sample required by the subject.

And (2) respectively fixing the sample and the ultrasonic rolling head on a machine tool.

Step (3), turning on the ultrasonic rolling equipment in advance, and setting technological parameters, wherein the technological parameters are as follows: current 2A, frequency 20Hz, amplitude 7 μm, load 300N.

Step (4), firstly operating the machine tool to enable the sample to do rotary motion, and then setting parameters of the machine tool, wherein the parameters are as follows: the main shaft rotating speed is 100r/min, and the feeding speed is 0.1 mm/r.

Drilling a hole in the workpiece, hanging the workpiece in an injection-infiltration furnace by using an iron wire to penetrate through the hollow hole, carrying out high-energy ion injection-infiltration of tungsten on the sample in the injection-infiltration furnace, and then carrying out carburizing heat treatment; a Dievar hot work die steel sample with the size of 30mm multiplied by 100mm multiplied by 10mm and a pure tungsten wire source electrode are arranged in a vacuum container. By using the principle of abnormal glow discharge of a barrel cathode, substances to be permeated are changed into high-energy ions, and a permeation layer is formed on the surface layer of a metal matrix; argon is introduced into a large-scale closed ion carburizing furnace to enable the facilities and the sample in the furnace to be in an argon atmosphere, the argon in the furnace is ionized into ions through abnormal glow discharge of a barrel-shaped cathode, the tungsten rod placed with the argon ions in high-speed motion impacts to enable the tungsten rod to generate tungsten ions, the tungsten ions generated by impact have high kinetic energy, impact the surface of the sample, are finally injected into the sample, then are carburized, and generate tungsten carbide in situ in the sample.

And (6) adjusting the voltage to 600V to keep the temperature in the furnace at the appropriate temperature of 470 ℃, so that a good infiltration injection effect can be achieved, and the crystal grains of the workpiece can not be coarse.

And (7) keeping the temperature for 24 hours. When the technological parameters are not changed, the heat preservation time is increased to improve the injection effect.

Carrying out ultrasonic surface rolling treatment on the sample, wherein the ultrasonic impact frequency is 20KHz, and the ultrasonic impact strength is 10s/cm²The hardness of the working head with the balls at the front end of the actuating mechanism is not lower than 900 HV. It is worth noting that the cooling liquid lubrication is carried out in the test process, and the test shows that the oil cooling effect is better.

The method comprises the steps of installing an actuating mechanism and mechanical parts on a machine tool, utilizing the feeding of the actuating mechanism driven by the machine tool and rolling pressure provided by a pressure spring at the bottom of the actuating mechanism, transmitting pressure and high-frequency impact vibration to the surface of the mechanical parts driven by the machine tool to rotate by the machine tool by a working head with balls at the front end of the actuating mechanism, wherein the high-frequency impact vibration is mechanical vibration which is obtained by converting alternating current into the same frequency by utilizing the special performance of piezoelectric ceramics, concentrating energy by gathering ultrasonic energy by an ultrasonic amplitude transformer with an energy gathering effect, amplifying the displacement of the mechanical vibration brought by an energy converter by the amplitude transformer, and enabling a processed material to generate elastic deformation and plastic deformation by utilizing the characteristic that metal has cold shrinkage property at normal temperature.

Example 2

A surface nano high-energy ion injection-infiltration composite treatment method comprises the following steps:

drilling a hole in the workpiece, and hanging the workpiece in the injection infiltration furnace by using an iron wire to penetrate through the hollow hole;

the voltage is adjusted to 600V to keep the temperature in the furnace at the proper temperature of 470 ℃, so that not only can a good infiltration injection effect be achieved, but also the crystal grains of the workpiece can not be coarse;

the heat preservation time is 24 h.

The method comprises the following steps that in the embodiment 1, a sample is prepared by adopting a process of ultrasonic surface rolling and high-energy ion impregnation tungsten carbide compounding;

example 2a sample was made using a single process of high energy ion-impregnated tungsten carbide.

And (3) evaluating the effect: by analyzing fig. 1 to 4, the grain structure of the surface of the sample of example 1 was more finely dense and the depth of injection of tungsten carbide was increased by 26.85% compared to the sample of example 2.

The surface hardness of example 1 was 945HV, a 4-fold increase over the hardness of the untreated base material, and a 31.13% increase over the surface hardness of the sample of example 2. In addition, the sample of example 1 had a lower average coefficient of friction and wear volume under high temperature frictional wear test conditions than the sample of example 2.

While the invention has been described above with reference to an embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the various features of the embodiments disclosed herein may be used in any combination, provided that there is no structural conflict, and the combinations are not exhaustively described in this specification merely for the sake of brevity and conservation of resources. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (1)

1. A surface nanocrystallization high-energy ion injection-infiltration composite treatment method is characterized by comprising the following steps:

(1) pretreatment before rolling of sample surface

Firstly, cutting an iron plate into a cylinder with the diameter of 10mm and the thickness of 12mm by utilizing wire cutting;

fixing a sample on a grinding machine, polishing, firstly polishing the sample flatness on one surface of the sample until the surface is flat, then polishing the surface flatness on the other surface, and finally performing fine grinding treatment on the surface to reduce the roughness of a rolled surface;

(2) ultrasonic rolling treatment of sample surface

Fixing the sample treated in the step (1) on a machine tool, and adjusting the coaxiality and the flatness of the sample;

firstly, operating a machine tool to enable a sample to do rotary motion, then starting rolling equipment to set corresponding parameters, waiting for about 5 minutes to enable the vibration frequency of ultrasonic equipment to reach a positive sine wave form, and finally applying pressure to a rolling head, wherein the machine tool parameters are 2-10A, the rotating speed of a main shaft of the machine tool is 100r/min, the feeding speed of the machine tool is 0.1mm/r, the vibration frequency of the ultrasonic equipment is 20-27KHz, the amplitude is 6.5-7.5 mu m, and the pressure applied by the rolling head is 300N;

(3) preparation of tungsten carbide composite layer

Drilling the workpiece processed in the step (2), and suspending the workpiece in an injection infiltration furnace by using an iron wire to penetrate through the hollow hole;

the voltage is adjusted to 600V to keep the temperature in the furnace at the proper temperature of 470 ℃, so that not only can a good infiltration injection effect be achieved, but also the crystal grains of the workpiece can not be coarse;

the heat preservation time is 24 h.

Images